BOSTON — Activists working to shut down the Pilgrim Nuclear Power Station gathered Thursday at the Statehouse to press for the immediate closure of the facility in Plymouth.

The protest comes after the owners, Entergy Corp., announced plans to close Massachusetts’ only nuclear power plant by June 2019.

That’s not soon enough for activists who have lobbied for years to close the plant.

When Entergy made its announcement, Diane Turco, executive director of Cape Downwinders, said the group cheered for “about 10 seconds until we heard ‘2019.’ ” She called it “nonsense.”

“That is a narrative that we reject,” she said. “The real narrative is that it will continue to operate a degraded and dangerous nuclear reactor until 2019, and that is unacceptable.”

Mary Lampert, of the group Pilgrim Watch, also spoke at the protest. Lampert said she fears Entergy won’t properly maintain a plant it is planning to close.

“We are clearly in the most dangerous period we have ever been in,” Lampert said.

The group also delivered a letter to Gov. Charlie Baker’s office calling on him to urge the Nuclear Regulatory Commission to shutter the plant.

Entergy officials have said cutting safety corners isn’t an option and the plant’s neighbors have no reason worry.

Last week’s closure announcement came about a month after federal inspectors downgraded the plant’s safety rating to the lowest level and said they would increase oversight in the wake of a shutdown during a winter storm.

Entergy officials maintain the plant remains safe, although it needed millions of dollars in upgrades. They also cited “poor market conditions, reduced revenues and increased operational costs” in their decision to close Pilgrim.

The 680-megawatt plant, which went online in 1972, was relicensed in 2012 for an additional 20 years. It employs more than 600 people.

The timing of the shutdown depends on several factors, including further discussion with ISO-New England, the operator of the region’s power grid. Entergy could close the plant as early as the spring of 2017 if it decides not to go through with a scheduled refueling. Protesters said the plant should not undergo another refueling.

Baker has said the anticipated 2019 closure of Pilgrim gives the state time to make the transition to other energy sources – such as wind, solar, hydropower and natural gas.